Protractor.



No. 667,264. Patented Feb. 5, l90l. F. A. TIBBALS.

PROTRACTOR.

(Application filed June 14, 1900.)

(No Model.)

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UNITED STATES PATENT FFICE.

FRANK ARTHER TIBBALS, OF LYNN, MASSACHUSETTS.

PROTRACTO R.

SPECIFICATION forming' part of Letters Patent No. 667,264, datedFebruary 5, 1901.

Application filed J 1116 14, 1900- To all whom it may concern:

Be it known that I, FRANK ARTHER TIB- BALS, a citizen of the UnitedStates, residing at Lynn, in the county of Essex and State ofMassachusetts, have invented certain new and useful Improvements inProtractors; and I do hereby declare the following to be afull, clear,and exact description of the invention, such as will enable othersskilled in the art to which it appertains to make and use the same.

This invention relates to protractors and rulers; and it consists in thenovel construction and combination of the parts hereinafter fullydescribed and claimed.

In the drawings, Figure l is a plan View of the instrument. Fig. 2 is aside view. Fig. 3 is a cross-section taken on the line w x in Fig. 1.

A is one arm of the protractor or ruler, which is provided with atubular socket B at one end, formed on a circular arc having its centerat b, which is one end of the arm A. O is the other arm of theprotractor or ruler, which is provided with an oliiset bar 0, which isformed on the same circular arc as the socket B and which is slidablewithin it. One end of the arm Cis arranged at the point I), so that thearms may be set at any angle and will always converge to the point I).As

Serial No. 20,330. (No model.)

the bar 0 is offset at c from the under side of the arm 0, the two armsalways lie in the same plane. The bar 0 is provided with a numberedscale d, which indicates the angle at which the arm 0 is set. Both armsA and O are provided with beveled ruling edges e.

The socket B has a cover-plate f, which is secured to it by rivets g,which pass through laterally projecting bosses g on the said socket andits cover.

G is a thumb screw or other approved clamping device for securing thebar in the socket, and thereby locking the said arms when set to anydesired angle.

What I claim is The combination, with an arm provided with a tubularsocket having a cover-plate secured to it on one side, said socket andplate having laterally-projecting bosses for the fastening devices; ofan arm provided with a curved bar which is slidable in the said socket,substantially as setforth.

In testimony whereof I affix my signature in presence of two witnesses.

FRANK ARTHER TIBBALS.

Witnesses;

ALICE J. MURRAY, FRED. K. DAGGETT.

